Mcarbocyanine dyes



Patented Dec. 17, 1946 r 2,412,815

a UNITED STATES PATENTOFFICE DICARBOCYANINE DYES John David Kendall and Harry Derek Edwards, Ilford, England, assignors to Ilford Limited, Ilford, England, a British company No Drawing. Application December 17, 1943, ?e11-19a;l3No. 514,667. In Great Britain January 4 Claims. (Cl. 260-240) 1 2 This invention relates to the production of dito compounds of general Formula D by treating carbocyanine dyes and particularly to the prothem with a sodium alkyl mercaptide and an duction of symmetrical dicarbocyanine dyes alkyl mercaptan under pressure. which are useful as optical sensitisers for silver Beta-alkyl-thio acrolein di-alkyl mercaptals halide photographic emulsions. 5 can be made by treating a compound of Formula In co-pending application Serial No. 514,666 A in which the groups R are alkyl groups with filed December 17, 1943, corresponding to British alkyl mercaptan in the presence of a basic conapplication No. 14/43, there is described the prodensing agent under pressure. duction of compounds of the general Formula I: According to the present invention, symmetri- XRl 0 cal carbocyanine dyestuffs are obtained by con- (I) densing a compound of general Formula I with XRl cyclic nitrogen compound containing a reactive where the groups R1 represent alkyl grou s a d methylene group (which term includes a methyl preferably ethyl groups, and the groups X are 15 or mono-substituted methyl group) substituted both oxygen atoms or both sulphur atoms. Comn the -posit t0 t q t a y t yc i pounds of the general Formula I can be made, nitrogen atOm- V as described in the aforesaid application by treat- The course of the reaction is believed to be as ing with an alkyl mercaptan, in the presence of follows:

I IXRI $2 F D- -'F' 1 i'-c11=on-c Etc-62 TDD: XR R/ \A N=-=-Q l I :1 a

| I Rs '5 f I fie lei "1 R2 r" "1 N--(5=C-CH=CHOH=C-C 1' I HA men zitlxn n a Re A an acid condensing agent, a compound of one of In the foregoing formulae R2 and R3 represent the Formulae A, alkyl or aralkyl groups, R3 may also be an un SR saturated aliphatic group, e. g. allyl, or a sub OHzCEFCfi (A stituted alkyl group, e. g. hydroxyalkyl, D represents the residue of a heterocyclic nitrogen SR nucleus and A represents an acid radicle. OR 40 Examples of heterocyclic nitrogen compounds fl which may be employed are quaternary salts contaming the necessary reactive methylene (or 0R methyl or mono-substituted methyl) group deon r rived from the following heterocyclic nitrogen (C 40 compounds: substituted and unsubstituted thiazoles,th1azol1nes, oxazoles, oxazolmes, selenazoles, OR selenazolines, pyridine, quinoline, indolenine, di- OR azines (e. g. pyrimidine and the diazines de- (D) scribed in British patent specification No. 425,- OR 50 609), thiodiazoles and quinazoline and the corresponding substituted and unsubstituted. polyor by treating with an alkyl mercaptan in the cyclic compounds such as the benzthiazoles,

pr n f a baslc c n ensin a ent und r Pres- 'naphthathiazoles and anthrathiazoles and the Sure, a o pound of Formula A. corresponding polycyclic oxazoles and selenazoles.

C'q p u d f h e a Formula A y be M Such heterocyclic compounds may contain subta d y br mmatm a r le n and atin stituent rou s in the benzene nuclei, e. g. alkyl, the product with an alkyl mercaptan followed by aryl, amino, hydroxy and alkoxy groups or haloheating with an. alkali to remove bromine. Comgen atoms.

pounds of general Formula B may be converted The quaternary salts may be derived from varian alkyl or aralkyl quaternary salt of a hetero-.

ous organic or inorganic acids, for example, they may be chlorides, bromides, iodides, alkyl sulphates, p-toluene sulphonates or perchlorates.

In carrying out the condensation using a com pound of general Formula I where X is oxygen, it is generally convenient to heat the reagents together in the presence of a base and a solvent; pyridine is excellent in serving both purposes. When carrying out the condensation using a compound of general Formula I where X is sulphur, however, it is preferred to heat the reagents together in the presence of a solvent and a substance which will combine with alkyl mercaptan split off during the reaction (a suitable medium is acetic anhydride which serves both purposes) and to finish oil the reaction by adding a base and heating for a further period.

The following examples illustrate the invention:

- I EXAMPLE I Preparation of 2':2'-diethyl thiadicarbocyanine iodide 3.05 gms. of l methylbenzthiazole ethiodide, 1.11 gms. of fi-ethyl-thio acrolein diethyl acetal and 15 ccs. of pyridine were mixed and boiled gently under reflux for 15 minutes. The reaction mixture was then poured into an aqueous solution of potassium iodide. The dye was precipitated and was filtered off, and washed with ethyl alcohol and ether. Recrystallisation from methyl alcohol solution yielded the dye as green needles. M. pt. 248 C. with decomposition. The dye had the structural formula:

EXAMPLE II Preparation of 1 :1'-diethyl 2:2"-quinodicarbocyanine iodide 1.5 gms. of quinaldine ethiodide, 0.6 gm. of ,8- ethyl thio acrolein diethyl mercaptal and cos. of acetic anhydride were boiled gently under reflux until partly in solution. 0.7 cc. of triethylamine was then added and the heating continued for IO-minutes. The reaction mixture was cooled and the dye precipitated by dilution with ether. The liquors were decanted through a filter and the residue lixiviated with water. The dye was filtered off and washed well with ethyl alcohol and ether, being thus obtained as green crystals with a bronze reflex. M. pt. 245 C. (with decomposition), and giving a turquoise blue solution in alcohol. The dye had the structural formula:

LCH-CH=OHCH=CH and 10 ccs. of acetic anhydride were boiled gently under reflux until partly in solution. 0.7 cc.

r under reflux.

' cc. of triethylamine and the heating continued of triethylamine was then added, and the reaction mixture stirred. The boiling was fooiotinued EXAMPLE IV Preparation of 3:3'-dimethyl-thiazolino dicarbocyanine iodide 1.12 gms. of 2-methyl thiazoline methiodide, 1.0 gm. of ,B-ethyl-thio-acrolein-mercaptal, and 15 ccs. of acetic anhydride were boiled gently To the solution was added 0.35

for six minutes. The reaction mixture was allowed to cool, lixiviated with petroleum ether, the petroleum ether decanted off, and the residue diluted'with ether. The precipitated dyestufi was filtered off and washed with ethyl alcohol,

water, ethyl alcohol again and finally ether, and was obtained as silvery crystals. M. pt. 202? C. with decomposition. Th dye had the structural As already stated, the dyestuffs obtained by the process of this invention are valuable sensitisers for photographic silver halide emulsions. Thus, for example, the dyestufi of Example IV supra incorporated in a silver iodobromide emulsion, extends the sensitivity to about 6200 A. with a maximum sensitivity at about 5750 A.

What we claim is: V 1. Process for the production of dicarbocyanine dyes which comprises condensing a compound of the general formula:

where the groups R1 are alkyl groups and the groups X are the same and selected from the class consisting of oxygen and sulphur atoms, with a compound selected from the class consisting of alkyl and aralkyl quaternary salts of heterocyclic nitrogen compounds containing a reactive methylene group in a-position to the quaternary heterocyclic nitrogenatom of the type usual in the cyanine dye art.

2. Process for the production of dicarbocyanine dyes which comprises condensing a compound or the general formula:

the groups X are the same and selected from in a-position to the qua-.

acrolein dialkyl acetal, with a compound selected 10 from the class consisting of alkyl and aralkyl quarternary salts of heterocyclic nitrogen compounds containing a reactive methylene group in a-IJOSitiOIl to the quaternary heterocyclic nitrogen atom of the type usual in the cyanine dye art, in the presence of a base and a solvent for the reactants.

4. Process for the production of dicarbocyanine dyes which comprises condensing B-ethyl-thioacrolein dialkyl mercaptal with a compound selected from the class consisting of alkyl and aralkyl quarternary salts of heterocyclic nitrogen compounds containing a reactive methylene group in u-position to the quarternary heterocyclic nitrogen atom of the type usual in the cyanine dye art, by heating the reagents together in the presence of a solvent and a substance which will combine with the alkyl mercaptan split oiT during the reaction, and then adding a base and continuing to heat the reagents for a further period.

JOHN DAVID KENDALL. HARRY DEREK EDWARDS. 

